iOS 5.1 code hints at simultaneous A5X and A6 processor development

Recent rumors have alternately suggested that Apple is working on a quad-core "A6" or an improved dual-core "A5X" processor for its next-generation mobile devices. But buried within the yet unreleased iOS 5.1 are references to two unreleased mobile processors, suggesting Apple is actually working on both at the same time.

As explained by 9to5 Mac, Apple's A4 processor has a model number of S5L8930X, while the A5 has a model number of S5L8940X. Note the last two digits differ by a value of 10. iOS 5.1 also contains references to processors with model numbers S5L8945X and S5L8950X. The numbers, with a difference of 5 and 10 respectively, suggest Apple is readying both an improved version of the A5, dubbed "A5X," and a complete redesign, believed to be the "A6."

The buzz about the next-generation mobile processor from Apple began to lean towards a quad-core design late last year. Apple's Xcode development environment added support for at least one quad-core ARM-based processor, and code references in iOS 5.1 pointed at quad-core support. A quad-core processor would certainly keep Apple competitive with high-end competing Android devices which have begun to incorporate quad-core processors such as NVIDIA's Tegra 3.

However, more recent rumors suggested that Apple's next-gen devices would be powered by a modified dual-core design, retaining the same basic CPU as the current A5 processor mated to an improved GPU design. The beefier GPU seems necessary to support a long-anticipated 2048x1536 pixel "Retina" display.

The fact that iOS 5.1 references two separate processors indicates Apple could have both in active development or even production. Apple's strategy may be to use an A5X for lower cost devices such as a low-end iPad or next-generation Apple TV. Or the A5X may be better suited to lower-power devices with smaller batteries, such as the iPhone or iPod touch, while a quad-core A6 would be better suited to the larger iPad.

Whatever strategy Apple is employing should be revealed soon enough, however, as Apple is expected to make an announcement concerning a third-generation iPad on or around March 7.